It is important to be able to engineer the brightness of interior spaces. In addition to the amount of light delivered to and reflected from surfaces in the space, light spectrum influences apparent scene brightness. Specifically, spaces illuminated by 'cool white' sources will look brighter than those illuminated by 'warm white' sources for the same photopic light levels. A scale model residential space was used to obtain judgements of scene brightness where light levels, surface reflectances and light source correlated colour temperatures were parametrically varied. Subjective and radiometric data were used to extend a provisional model of scene brightness, which is intended to be useful for predicting scene brightness of interior spaces illuminated to different levels by 'white' light sources of different correlated colour temperatures.